Hybrid automatic repeat request (HARQ) is a system of error checking where transmissions from mobile devices are checked for errors. If the transmission contains an error, a retransmission request is sent back to the mobile device to resend the transmission. In synchronous uplink systems, there are standards for scheduling so that a certain amount of time is allotted to send the retransmission requirement. The system that performs the HARQ has traditionally been the baseband unit of an eNodeB in an LTE system.
Due to increasing demand, small cell deployments are being developed with cloud radio access network (RAN) systems, where a portion of a base station device (e.g., the baseband unit device of the eNodeB) may support multiple remote radio unit devices. The remote radio unit devices, which are primarily used for transmission and reception of radio signals from mobile devices, may be located at some distance from the baseband units, physical or virtual, and so the increased latency due to the distance between the devices may negatively affect HARQ performance.